Replacing a stub shaft bearing for a hydroelectric turbine using a runner hub lifting device

Abstract

The stub shaft bearing for a stub shaft can be replaced while the stub shaft remains installed in a hydroelectric unit. A runner hub lifting device may be positioned within a discharge ring surrounding a runner hub. The runner hub lifting device may lift the runner hub, and a stub shaft bearing may be removed from a stub shaft. The stub shaft bearing may be disassembled into bearing sections while located in a chamber in the hydroelectric unit. The bearing sections may be removed from the chamber through a service hatch in the chamber. A replacement stub shaft bearing may be moved into the chamber and installed on the stub shaft. The runner hub lifting device may lower the runner hub.

What is claimed is: 
     
       1. A method for lifting a runner hub installed in a hydroelectric unit using a runner hub lifting device, comprising:
 moving the runner hub lifting device into a discharge ring of the hydroelectric unit, wherein the discharge ring surrounds a runner including the runner hub; 
 positioning the runner hub lifting device within the discharge ring so that a centerline of the runner hub lifting device is aligned with a centerline of the runner hub; 
 activating at least one hydraulic ram of the runner hub lifting device so that a hub support plate of the runner hub lifting device moves towards the runner hub and the hub support plate contacts the runner hub, wherein a top surface of the hub support plate is curved to match a curve of the runner hub; 
 fixing a bottom plate of the runner hub lifting device to an inner surface of the discharge ring below the runner hub; and 
 further activating the at least one hydraulic ram of the runner hub lifting device to lift the runner hub from a first position to a second position, 
 wherein the runner hub lifting device includes at least one base support mounted to the bottom plate, a ram base plate mounted to an end of the base support opposite the bottom plate, the at least one hydraulic ram mounted on the ram base plate, and the hub support plate mounted to the at least one hydraulic ram opposite the ram base plate, 
 wherein the runner hub lifting device further comprises at least one hub support, and 
 wherein the method further comprises inserting the at least one hub support between the ram base plate and the hub support plate when the runner hub reaches the second position. 
 
     
     
       2. The method of  claim 1 , wherein the hub supports are rods or L-shaped brackets. 
     
     
       3. The method of  claim 1 , wherein the ram base plate is rectangular and the hub supports are inserted at each corner of the ram base plate. 
     
     
       4. The method of  claim 1 , further comprising:
 prior to positioning the runner hub lifting device within the discharge ring, rotating runner blades of the runner hub into a position where the runner blades straddle the centerline of the runner hub.